(a) Field of the Invention
The present invention relates to an electrical connection device. Especially, the present invention relates to the structure improvement of the electrical connection device soldered on a main board by solder balls, wherein the device can be provided for inserting and placing an IC package.
(b) Description of the Prior Art
For long time, there are two ways that placing the Integrated Circuit (IC) Package on the Circuit Board (or Main Board). In one of the two ways, the IC is soldered fixedly on the main board and can not be removed. Another way the IC is replaceable. The replaceable electrical connecting device and the IC combining device are usually suitable in a IC package that needs upgrade sometimes or in a IC package with high price. In the case that one of the IC package broken and needs to be replaced, other packages can be kept. The best example is the socket and the circuit board connecting device that used for a Central Processing Unit (CPU).
Please refer to FIG. 1 and FIG. 2, which showing the typical replaceable IC package and the composition device of the electrical connecting device and the main board in the market. Conventionally, in order to maintain the excellent electrical connection and the replaceable-ness, the pins 111 are placed on the IC package 11 and the socket 13 with a plurality of pin holes 131 is set on the circuit board 12 to connect the IC package 11. In prior art, there are two package methods to pack an IC package, namely Lead Frame and Ball Grid Array (BGA). In recent years, the Flip Chip BGA Packaging is often used for an IC package that needs high efficiency and high number of pins. FIG. 1 is showing its basic devices, which comprising the IC chip 112 being placed on one side of the substrate 113 by the Flip Chip method, several solder balls 114 being placed on the another side of the substrate 113 that connected electrically to the chip 112 thru the circuit layout of the substrate 113, and the heat sink 115 is attached on the other side of the chip 112 that will not operate. Since the pin 111 is not hard and still enough, it is easy to be distorted and damaged during replacement. So in practice, a plurality of the pins 111 will be molded and fixed on a interposer 116 before it soldered on the solder ball 114.
Traditionally, the plugged-in electrical connection device 13 is composed of the following elements in order to maintain the replaceable feature. The elements include of the main board 12 on which there are the sockets 132 with a plurality of the pin hole 131, a slide 133 that can be moved linearly on top of the socket 132 and a pulling long stick 134 placed on the side of the socket 132 to drive the slide 133 to move slightly. There is electrical conducting holder 137 placed in each pin hole 131 on the socket 132. And the solder pad 135 is formed on the bottom part of the pin hole 131. The pin hole 131 is extended from the bottom part of the electrical conducting holder 137 to form the pins 1371 in order to provide several Plated Through Holes (PTH) 121 on the main board 12 to plug in. The electrical conducting layer 122 in the PTH 121 on the main board 12 provides the function of the electrical connection with the pins 1371. The position of the PTH 121 and the position of the upper contact pad 1221 on the upper surface of the main board 12 is defined by the SMD (Solder Mask Defined) or NSMD (None Solder Mask Defined). The pins 1371 and the electrical connection device 13 are soldered firmly on the main board 12 by using the solder 123 and the solder 125. Corresponding to the positions of the pin holes 131 on the slide 133 exist several bigger holes. Pulling down the pulling stick 134 and rotating it around the stick 136 until the pulling stick 134 being parallel with the socket 132 will make the slide 133 move slightly and hold the pins 111 of the IC device 11 tightly in the pin holes 131. When pulling out the IC device 11, the pulling stick 134 has to be moved until it making a 90 degree angle with the socket 132 to loose the pins 111 from the IC device 11 by the way.
Please refer to FIG. 3 and FIG. 4, which are showing another composition of the replaceable IC device and the electrical connection device and the main board. As shown, the structure of the IC device 11 in prior art is similar to the structure of the electrical connection device 13a in FIG. 1. The major difference is that the bottom part of the socket of the electrical connection device 13a in FIG. 3 is ball structure instead of pin structure. And the lower part of the electrically conducting holder 137a in the electrical connection device 13a is bent 90 degree to be the solder pad 139 which combines the solder ball 138. And instead of the PTH, the solder pad 126 is placed on the main board 12a. The solder ball 138 will be soldered firmly between the two solder pads 139 and 126 stably by performing the solder reflow on the solder ball 138 in the electrical connection device 13a and the solder pad 126 on the main board 12a. The disadvantages in prior art are that the solder pad 139 on the bottom part of the electrically conducting holder 137a in the electrical connection device 13a and the solder pad 126 on the main board 12a are flatly planar structures. So, the solder ball 138 and the solder pad 139 and 126 are combined plainly. The contact area is limited, the electrical characteristic is bad and the intensity of the structure of the combination is weaker. The disadvantages lead the rising of the defects of the products and sometimes the department of the solder ball 138. Also, the overflow of the solder ball 138 will lead the circuit shortage and the electrical instability. In the same time the disadvantage also includes the bad co-planarity between the electrical connection device 13a and the main board 12a. 
The primary aspect of the present invention is to provide an electrical connection device. By special design of geometry structure, the present invention will lead the strong intensity, the electrical characteristics and the co-planarity of the product, and the yield of the product after the solder reflow of the solder pad on the bottom part of the electrically conducting holder and the solder ball.
Another aspect of the present invention is to provide an electrical connection device which having a contact ring optionally on the bottom parts of the pin holes in the sockets to enlarge the contact area between the solder ball, the sockets and the electrically conducting holders.
The third aspect of the present invention is to provide an electrical connection device which having a contact ring optionally on the bottom parts of the pin holes in the sockets, and at least a portion of the contact ring is with difference in height with the solder pad on the bottom part of the electrically conducting holder, with this difference of horizontal altitude between the geometric structure, the present invention will enlarge the contact area between the solder ball, the sockets and the electrical conducting holders,
The fourth aspect of the present invention is to provide an electrical connection device. With increasing a additional convex part on the bottom surface of the pin holes in the sockets to contact the periphery of the solder pad on the bottom part of the electrically conducting holder, the present invention will avoid the solder material in siphon phenomenon between the electrically conducting holder and the pin holes in the solder reflow process. And because the additional convex part placed against the solder ball, which will avoid the electrical conducting holder from being released or removed that caused by the pushing force of the solder ball. In one of the embodiment of the electrical conducting device of the present invention, we increase the contact area of the solder ball and socket after the solder reflow process by the suitable geometrical design. Example that we design the solder pad on the bottom part of the electrical conducting metal to have the concave and convex part, the holes and the slope to produce the difference in height. Or we can increase a contact ring optionally in the area of the solder pad to create the difference of the heights between the contact ring and the solder pad to increase the contact area in the solder reflow process for the solder pad, the contact ring and the solder ball. And the solder ball will flow into the concave and convex part of the solder pad, the hole or the slope partly to achieve the effect of inlaying. And with the improvement described above, the contact area will be enlarged, the electrical characteristics, the intensity, the coplanarity and the yield will be better.